I don't have an HD-5500, but I'm pretty sure the audio jack is an output, not an input. It would be the analog audio output. You have to connect it to a soundcard to capture the analog audio. I don't know why they disable the cx23883's analog audio capture ability. Maybe Rusty can explain the why that's done.

Posted: Mon May 29, 2006 9:32 am

pcHDTV_tech

Joined: 16 Dec 2004

Posts: 295

I don't know why it's been designed that way. It's my understanding the CX23883 doesn't actually have audio capture (A/D converters) ability but allows for I2C inputs from an external audio codec. My guess (and that's just what it is) is that the design has always focussed on the HDTV side of the design and the NTSC design is a holdover from earlier designs.

The HD2000 card conflicts with the BT878 audio driver because the HD2000 used the same PCI device for video that other cards use for the audio function. That type of issue was resolved for the HD3000 and HD5500. I think somewhere along the line a choice was made to use the soundcard audio (external cable from HD3000/5500 audio out to sound card line in) instead of putting an audio codec on the board.

My $0.02

Rusty

Posted: Mon May 29, 2006 11:47 pm

xyzzy

Joined: 12 Feb 2006

Posts: 225

The cx23883 does have an audio A/D converter. It has two 10-bit A/D converters in fact. With an S-video input, one is used for luma and the other for chroma. With a composite input, like a tuner, one ADC is used for video and the other can be used for audio. In fact, the HD-3000 (and probably the HD-5500) do just this! See section 2.1.2 in the cx23880 datasheet.

When you get analog audio from the card, it not produced directly by the tuner (as in older bt848 designs) but by the cx23883 chip. It samples the audio with its high speed 10-bit A/D, does BTSC/NICAM/A2, etc. stereo decoding, and then outputs the sound via its built in stereo audio DACs. You can see in the driver, where the BTSC audio setup is done, a 12 dB gain is turned on for the chroma/audio ADC, various V4L2 controls use the cx88 to set audio volume and panning, and so on.

The only thing that is disabled is PCI function 1, that allows this audio, which is already being captured by the cs23883, to be transfered over the PCI bus.

The chip can also interface to an external ADC and/or DAC via I2S, but no one seems to use that feature. A TV card with an SPDIF port that could output dolby digital to a home theater receiver would be really nice. Getting a soundcard that can do DD output in linux is pain, but with a digital audio out on the TV card, you wouldn't even need a sound card at all to make a DVR.

Posted: Tue May 30, 2006 9:30 am

pcHDTV_tech

Joined: 16 Dec 2004

Posts: 295

I'll bring up this issue and see if anything can be done to turn this on easily. I'll see if I can get a datasheet on the cx23883. All I could find on Conexant's website was market fluff but I didn't search too hard.

Thanks,

Rusty

Posted: Wed May 31, 2006 9:03 pm

serrs

Joined: 25 May 2006

Posts: 11

Location: Pocatello, ID

Thanks xyzzy! Although I don't understand it all... I understand enough to know what to expect.

Rusty, I appreciate the effort to see if we can turn on internal analog audio functionality.

Digital Audio

Posted: Thu Jul 06, 2006 11:55 am

nybbler

Joined: 06 Jul 2006

Posts: 125

It looks like the bit to enable audio functionality is read/write ("for test purposes only") so eeprom hackery might not be necessary. But there's gotta be a catch, right?

Posted: Thu Jul 06, 2006 6:40 pm

pcHDTV_tech

Joined: 16 Dec 2004

Posts: 295

Actually, since this was brought up pcHDTV has begun shipping the HD5500 with the digital sound enabled. cx88-alsa is the driver you would want. For those few who got a card prior to this change (/sbin/lspci will tell you if you have an [Audio Port] device on your card or not) You can contact pcHDTV and they will swap your card for one with the change. Thanks to xyzzy for pushing the issue a little harder here.

Historically it was turned off in the HD3000 because there wasn't audio driver support for it under V4L. Most of the video cards that shipped back then had it turned off as well and they used the line-in trick. (At least according to the V4L Wiki) Hence, very few apps have been written to actually use the digital audio input from the computer bus. I understand mplayer will and Myth is supposed to. I haven't had much luck with either, but I was able to get the sound using arecord piped into aplay while tvtime was runing. More info on getting this running can be found at linuxtv.org under V4L Wiki -> Saa7134-alsa The sample rate setting is 48000 instead of 32000 used int he examples.

Hope this Helps,

Rusty

Posted: Thu Jul 06, 2006 7:22 pm

nybbler

Joined: 06 Jul 2006

Posts: 125

Hey, thanks, tech. I was just about to post that I'd tried it out with my new card and it works. Well, it crashes when changing channels but that's probably my very primitive "arecord | aplay" test configuration.

arecord -B 16000 -D hw:0 -c 2 -r 48000 -f S16_LE | aplay -D hw:1

Now there's no need for that annoying loopback cable and my two-tuner system can record two analog channels. Well, as soon as I get such trivialities as a motherboard, case, and power supply

Posted: Fri Jul 07, 2006 4:20 am

xyzzy

Joined: 12 Feb 2006

Posts: 225

Since audio is actually can work, I got motivated to look into fixing the eeprom.

I've written a program that will modify the card's eeprom to enable or disable the audio port. I tested it with my HD-3000 and it works!

There shouldn't be any need to go to the trouble to send your card in to swap with a different one, unless there are different versions out there with write-protected eeproms.

Posted: Fri Jul 21, 2006 5:50 pm

cfr131

Joined: 21 Jul 2006

Posts: 13

pcHDTV_tech wrote:

Actually, since this was brought up pcHDTV has begun shipping the HD5500 with the digital sound enabled. cx88-alsa is the driver you would want. For those few who got a card prior to this change (/sbin/lspci will tell you if you have an [Audio Port] device on your card or not) You can contact pcHDTV and they will swap your card for one with the change. Thanks to xyzzy for pushing the issue a little harder here.

I got a card very early; I have no lspci in /sbin? Probably distro dependent, which is something I am still learning. I do have it in /bin/usr but there is no cx88-alsa on the list. Does that mean I should send the card in to get the update?

Posted: Tue Oct 17, 2006 12:08 pm

cfr131

Joined: 21 Jul 2006

Posts: 13

I have the analog sound working, but the quality is very bad. It sounds like a 56kbs MP3, with lots of compression artificts. I don't know where to look to see why there is compresion occuring.

The other problem is that in Myth, when switching channels, I lose analog sound.